The mound measures roughly 5.4 metres from north to south and 2.5 metres east to west, and within it lies a drystone chamber, a souterrain, of the kind that appears throughout early medieval Ireland and is understood to have served as a place of refuge, concealment, or cool storage. The chamber here is at least 2.7 metres long but only about half a metre wide, roofed by heavy capstones sitting around a metre above the floor. The northern end is now blocked by collapse, and a small vent in the roof, barely 20 by 15 centimetres, is the only concession to air or light from above. Beyond the entrance to the south, the side walls continue for a further 1.8 metres without any roofing, suggesting a kind of forecourt or approach corridor that was always open to the sky.

Souterrains, which are essentially underground stone-built tunnels or chambers constructed without mortar, are found across Ireland in their hundreds, typically associated with early Christian period settlements between roughly the sixth and twelfth centuries. They were built to be entered crawling, and the narrowness of this example, scarcely wider than a person's shoulders, is consistent with that deliberate inconvenience. The site on the Dingle Peninsula was documented by J. Cuppage in the 1986 archaeological survey of the Corca Dhuibhne region, a thorough inventory of the extraordinary concentration of prehistoric and early historic monuments found along this westernmost stretch of Kerry. The marshy ground beside the Garfinny river would have made the site both harder to approach uninvited and easier, perhaps, to defend or abandon quickly.